( function () {
/**
 * Blend two textures
 */
const BlendShader = {
  uniforms: {
    'tDiffuse1': {
      value: null
    },
    'tDiffuse2': {
      value: null
    },
    'mixRatio': {
      value: 0.5
    },
    'opacity': {
      value: 1.0
    }
  },
  vertexShader:
  /* glsl */
  `

		varying vec2 vUv;

		void main() {

			vUv = uv;
			gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );

		}`,
  fragmentShader:
  /* glsl */
  `

		uniform float opacity;
		uniform float mixRatio;

		uniform sampler2D tDiffuse1;
		uniform sampler2D tDiffuse2;

		varying vec2 vUv;

		void main() {

			vec4 texel1 = texture2D( tDiffuse1, vUv );
			vec4 texel2 = texture2D( tDiffuse2, vUv );
			gl_FragColor = opacity * mix( texel1, texel2, mixRatio );

		}`
};

THREE.BlendShader = BlendShader;
} )();
